Botany: a record-breaking pollen catapult

The release of stored elastic energy often drives rapid movements in animal systems, and plant components employing this mechanism should be able to move with similar speed. Here we describe how the flower stamens of the bunchberry dogwood (Cornus canadensis) rely on this principle to catapult pollen into the air as the flower opens explosively. Our high-speed video observations show that the flower opens in less than 0.5 ms--to our knowledge, the fastest movement so far recorded in a plant.     

Botany: floral fluorescence effect

The way flowers appear to insects is crucial for pollination. Here we describe an internal light-filtering effect in the flowers of Mirabilis jalapa, in which the visible fluorescence emitted by one pigment, a yellow betaxanthin, is absorbed by another, a violet betacyanin, to create a contrasting fluorescent pattern on the flower's petals. This finding opens up new possibilities for pollinator perception as fluorescence has not previously been considered as a potential signal in flowers.     

Botany: specialized bird perch aids cross-pollination

Birds may hover over or perch on flowers when feeding on nectar, and this assists cross-pollination if they then visit other plants. Here we investigate the curious sterile inflorescence axis of the South African Cape endemic 'rat's tail' plant (Babiana ringens, Iridaceae), whose function--unlike in other bird-pollinated plants--is exclusively to provide a perch for foraging birds. We find that this structure promotes the plant's mating success by causing the malachite sunbird (Nectarinia famosa), its main pollinator, to adopt a position ideal for the cross-pollination of its unusual ground-level flowers.     

校园绿化与植物学教学

植物学是一门实践性很强的学科 ,因其教学内容跨度大、涉及面广、课时少 ,使教学内容受到一定影响 ,本文针对这些问题进行了教学改革 ,利用校园植物进行植物学教学 ,有效地提高了教学质量。     

生态系统关键种理论:新思想、新机制、新途径

关键种概念的提出,推动了生态学的深入发展,并渐已成为保护生物学基本原理的组成部分,但同明它也受到一些质疑介绍了关键种概念的内涵、外延及国内外研究现状,评价了其重要价值,阐述了亟待研究的几个问题。     

Opsin expression: new mechanism for modulating colour vision

Each cone photoreceptor in the retina responds to light in a limited range of wavelengths, giving it a spectral phenotype. This phenotype is determined by the most prevalent of the photoreceptor's visual-pigment proteins (opsins) and is assumed to remain unchanged during an animal's lifetime. Here we show that in the Pacific pink salmon, Oncorhynchus gorbuscha, single cones can switch their spectral phenotype from ultraviolet to blue by regulating the production of the appropriate opsins as the fish grow older. This photoreceptor plasticity may operate to modulate colour vision as the salmon's lifestyle changes.     

一种新型微位移放大机构设计与特性分析

基于柔性铰链的传导性,运用杠杆原理设计了一种全对称结构的二级微位移放大机构,该机构具有无附加方向上位移及运动精确等优点.建立了微位移放大机构的仿真模型和运动学模型,给出了工作原理;根据机构学原理推导出了机构位移放大比,运用ANSYS13.0对该机构进行有限元仿真,得出了实际输出位移、放大比及该机构的固有频率.放大比误差为7.46%;误差分析主要原因为在理论模型中采取简化分析,忽略了柔性铰链伸长变形导致的中心偏移,并且假设了除去柔性铰链外,其他的部分全为刚性.本文研究为微位移放大机构的实际生产提供了理论依据.     

一种新型齿轮齿条发动机的结构及其机理分析

提出一种能源利用率高的新型齿轮齿条发动机,介绍该发动机的结构和特点,分析发动机的工作过程及其驱动特性.理论分析和仿真实验结果表明,新型发动机解决了传统发动机存在对曲轴主轴颈的死点压力和对汽缸壁的侧向压力等不平衡问题.     

植物学中的探究式教学

文章论述了探究式教学与创新教育的关系；讨论了探究式教学对创新人才培养的意义以及植物学中怎样应用探究式教学。     

Structures of human insulin-degrading enzyme reveal a new substrate recognition mechanism

Insulin-degrading enzyme (IDE), a Zn2+-metalloprotease, is involved in the clearance of insulin and amyloid-beta (refs 1-3). Loss-of-function mutations of IDE in rodents cause glucose intolerance and cerebral accumulation of amyloid-beta, whereas enhanced IDE activity effectively reduces brain amyloid-beta (refs 4-7). Here we report structures of human IDE in complex with four substrates (insulin B chain, amyloid-beta peptide (1-40), amylin and glucagon). The amino- and carboxy-terminal domains of IDE (IDE-N and IDE-C, respectively) form an enclosed cage just large enough to encapsulate insulin. Extensive contacts between IDE-N and IDE-C keep the degradation chamber of IDE inaccessible to substrates. Repositioning of the IDE domains enables substrate access to the catalytic cavity. IDE uses size and charge distribution of the substrate-binding cavity selectively to entrap structurally diverse polypeptides. The enclosed substrate undergoes conformational changes to form beta-sheets with two discrete regions of IDE for its degradation. Consistent with this model, mutations disrupting the contacts between IDE-N and IDE-C increase IDE catalytic activity 40-fold. The molecular basis for substrate recognition and allosteric regulation of IDE could aid in designing IDE-based therapies to control cerebral amyloid-beta and blood sugar concentrations.     

口试——植物学课程考核方式的有益尝试

根据素质教育的理论,沈阳农业大学植物实验室改革植物学传统笔试的考核方法,尝试了口试的形式.经过两年的实践,证明采用口试的方法较笔试有诸多优点,尤其对考查学生综合运用知识分析问题、解决问题的能力,对考查学生的动手能力等方面是笔试无法比拟的.在考试这一重要的教学环节中,是实践素质教育的一种良好形式.文中也分析了口试的不足之处并提出进一步完善的措施.     

汽车新型储能动力传动系统节能机理

储能传动是一有效的节能传动技术。研究了一种新型储能动力传动系统。与传统的储能动力传动系统相比，新型储能动力传动系统的结构更简单，重量更轻，并且性能更加优越。在探讨新型储能动力传动系统的原理之后，对该系统进行了性能分析，给出了一个新型储能动力传动系统的仿真实例。     

开设药用植物学设计性实验的思考与体会

阐述了开设药用植物学设计性实验的意义,针对设计性实验的特点,开展药用植物学设计性实验的实践,总结了开设性的做法和体会。     

半开放式植物学实验教学模式初探

为了培养学生的综合能力和学习兴趣,作者在植物学实验中应用半开放式教学模式,在实验室条件允许的基础上,由学生自主选择材料和内容,自己设计并操作实验,教师参与其中起引导和辅导作用,及时将实验情况反馈给学生,促使学生不断改进,取得了较好的效果,学生独立自主学习的能力和兴趣明显提高,思维能力有所扩展。     

《药用植物学》授课实例与体会

以《药用植物学》中被子植物门山茱萸科植物山茱萸为例,以完成教学大纲要求为基本原则,结合多年教学实践和感受,从说课、教法、学法和课件制作等方面进行探讨。实践证明,此举不仅有助于教师教学水平的提高,还能调动学生的主动性,提高教学质量。     

对加强植物课实践教学的探索

本文对植物课如何加强实践教学提出自己做法及见解,并对今后如何进一步充实、改革、不断提高实验、实习的质量和水平进行了探讨。